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This paper discusses the poisoning of a selective catalytic reduction (SCR) catalyst by trace levels of platinum originating from an upstream diesel oxidation catalyst (DOC). A diesel aftertreatment system consisting of a DOC, urea based SCR Catalyst and a DPF was aged and evaluated on a 6.4 liter diesel engine dynamometer. The SCR catalyst system consisted of an Fe-zeolite catalyst followed by a Cu-zeolite catalyst. After approximately 400 hours of engine operation at varied exhaust flow rates and temperatures, deactivation of the SCR catalyst was observed. A subsequent detailed investigation revealed that the Cu catalyst was not deactivated and the front half of the Fe-based catalyst showed severe deactivation. The deactivated portion of the catalyst showed high activity of NH3 conversion to NOx and N2O formation. The cause of the deactivation was identified to be the presence of trace Pt contamination.

Passive in-line catalyzed hydrocarbon (HC) traps have been used by some manufacturers in the automotive industry to reduce regulated tailpipe (TP) emissions of non-methane organic gas (NMOG) during engine cold-start conditions. However, most NMOG molecules produced during gasoline combustion are only weakly adsorbed via physisorption onto the zeolites typically used in a HC trap. As a consequence, NMOG desorption occurs at low temperatures resulting in the use of very high platinum group metal (PGM) loadings in an effort to combust NMOG before it escapes from a HC trap. In the current study, a 2.0 L direct-injection (DI) Ford Focus running on gasoline fuel was evaluated with full useful life aftertreatment where the underbody converter was either a three-way catalyst (TWC) or a HC trap. A new HC trap technology developed by Ford and Umicore demonstrated reduced TP NMOG emissions of 50% over the TWC-only system without any increase in oxides of oxygen (NOx) emissions.

This paper summarizes results from a study on the effects of aging temperature and A/F ratio on the NOx storage capacity of a lean NOx trap. When aged at stoichiometry at 700°C, the NOx storage capacity of the NOx trap dropped considerably during the first 200 hours of aging and then at a much slower rate beyond 200 hours. The NOx storage capacity dropped more rapidly as the aging temperature increased, with the drop in capacity particularly evident between 900°C and 1000°C. The drop in NOx capacity was significantly larger for samples aged with part-time lean operation and/or part-time rich operation than for samples aged continuously at stoichiometry. The detrimental effects of lean and rich operation increased as the temperature increased. A Pt/Al2O3 model catalyst was exposed to reducing conditions at temperatures ranging from 670°C to 1041°C and then to oxidizing conditions over the same temperature range, and in-situ XRD was used to investigate Pt particle coarsening.